Method for monitoring a conveyor belt and system therefor

Abstract

The invention relates to a method for monitoring a continuous revolving conveyor belt (4) having a connecting region (8). The connecting region (8) is monitored with the aid of two transponders (12) and (14). One of the transponders is arranged forward of the connecting region (8) and the other transponder is connected rearward of the connecting region (8). Both transponders (12) and (14) transmit respective signals to an external transmitter/receiver unit 16 wherein a conclusion is drawn as to the spacing of the two transponders (12) and (14) on the basis of the time-dependent spacing of the two signals. If the spacing s of the transponders (12) and (14) exceeds a pregiven amount, then a conclusion is drawn by the external transmitter/receiver unit (16) as to a critical change in length of the connecting region (8) and corresponding measures are initiated.

What is claimed is: 
     
       1. A method of monitoring a continuous revolving belt, said belt including a connecting section having a start and an end delimiting the length of said section viewed in the direction of movement of said belt, said start and said end assuming a pregiven desired distance s des  therebetween measured along said section when said belt is in an unloaded, undamaged state, the method comprising the steps of: providing at least one start transponder mounted in or on said belt at said start of said connecting section and at least one end transponder mounted in or on said belt at said end of said connecting section;   providing an external transmitter/receiver unit having an operative region wherein signals from said transponders can be received thereby;   transmitting a first signal from said start transponder to said external transmitter/receiver unit at time point t 0  when said start transponder passes through said operative region;   transmitting a second signal from said end transponder to said external transmitter/receiver unit at time point t 1  when said end transponder passes through said operative region;   determining a time interval dt act  =t 1  -t 0  in said external transmitter/receiver unit; and,   determining whether a critical change in length of said connecting section has occurred based on said time span dt act .   
     
     
       2. The method of claim 1, comprising the further step of initiating measures based on whether a critical change in length has occurred. 
     
     
       3. The method of claim 1, wherein each of said transponders transmits the signal corresponding thereto in the form of an individual identifier. 
     
     
       4. The method of claim 1, wherein said belt is a conveyor belt. 
     
     
       5. The method of claim 1, comprising the further steps of: providing an additional transponder in or on said belt in spaced relationship to one of said start transponder and said end transponder so as to cause said additional transponder and said one transponder to conjointly define a virtually unchangeable distance s ref  therebetween;   transmitting an additional signal from said additional transponder to said external transmitter/receiver unit at a time point t 2  when said additional transponder passes through said operative region;   transmitting a signal from said one transponder to said external transmitter/receiver unit at time point t 3  when said one transponder passes through said operative region;   computing the time span dt'=t 3  -t 2  in said external transmitter/receiver unit and, from said time span dt', computing the speed v=s ref  /dt' of said belt;   computing the product of said time span dt act  and said speed v to obtain the actual distance s act  =vdt act  between said start transponder and said end transponder; and,   initiating measures when the actual distance s act  differs from said pregiven desired distance s des  by more than a pregiven amount ds.   
     
     
       6. The method of claim 5, wherein each of said transponders transmits the signal corresponding thereto in the form of an individual identifier. 
     
     
       7. The method of claim 1, comprising the further steps of: providing an additional transponder in or on said belt in spaced relationship to one of said start transponder and said end transponder so as to cause said additional transponder and said one transponder to conjointly define a virtually unchangeable distance s ref  therebetween;   transmitting an additional signal from said additional transponder to said external transmitter/receiver unit at a time point t 2  when said additional transponder passes through said operative region;   transmitting a signal from said one transponder to said external transmitter/receiver unit at time point t 3  when said one transponder passes through said operative region;   computing the time span dt'=t 3  -t 2  in said external transmitter/receiver unit and then, also in said external transmitter/receiver unit, computing the ratio dt act  /dt'; and,   initiating measures when said ratio dt act  /dt' differs from a ratio of s des  /s ref  by more than a pregiven amount.   
     
     
       8. The method of claim 7, wherein each of said transponders transmits the signal corresponding thereto in the form of an individual identifier. 
     
     
       9. A system for monitoring a continuous belt revolving in a direction of movement and including a connecting section having a start and an end delimiting the length of said connecting section viewed in the direction of movement of said belt, the system comprising: an external transmitter/receiver unit having an operative region wherein signals can be received;   a start transponder mounted in or on said belt at said start of said section and transmitting a first signal to said external transmitter/receiver unit when passing through said operative region thereof;   an end transponder mounted in or on said belt at said end of said section and transmitting a second signal to said external transmitter/receiver unit when passing through said operative region thereof;   said external transmitter/receiver unit being programmed to compute a time span dt act  between which said first and said second signals are received thereby; and,   said external transmitter/receiver unit being programmed to compute, based on said time span dt act , whether a critical change of length of said connecting section has occurred.   
     
     
       10. The system of claim 9, wherein said belt is a conveyor belt.